As the number of subscribers for telephone, interne and video services continues to grow throughout the world, so does the need to support and maintain such services, as well as the devices forming part of a communications network. Many believe that to keep up with the accelerated demand for such services, current strategies for using and developing known protocols require further development.
A new paradigm of testing the quality of services delivered over a network is to conduct such testing by remotely accessing a subscriber site. Remote access has several advantages, including increasing availability, efficiency, and affordability. However, the application of the MGCP/NCS protocol to a test device acting as or behind a gateway, to initiate a connection in loopback mode with a remote endpoint device located on a subscriber's site, such as an MTA has not been disclosed in the prior art. Indeed, the IETF RFC 3435 MGCP and the PacketCable NCS specifications, which describes a master slave protocol, does not foresee such application.
Loopback-based testing is an obvious and classical way to test the quality of transmission on the path used to carry media over networks which use different technologies. Because of the complexity and time required to migrate media transport from various technology-based networks to a single technology transport packet-based network, hybrid networks proliferate. Accordingly, there is a pressing need for new techniques to test the quality of integrated services over hybrid networks, in an economically efficient manner.
As shown in the prior art, general network architecture consists of a packet-based core network interconnecting various access networks via appropriate gateways. Media Gateway Control Protocol (MGCP) and its variation Network-based Call Signalling (NCS) were developed in order to control the different gateways within the packet-based networks. MGCP/NCS is a signalling protocol based on the Internet Protocol (IP) controlling a master slave dialog, where the master is the Call Agent (CA) or Call Management Server (CMS), commonly integrated in a smart switch (sometimes referred to as a “soft switches”). The slaves are the gateways. The CA creates connections between endpoints which negotiate media session parameters via Session Description Protocol (SDP). MGCP/NCS describes different connection modes, depending on the connection purpose and the call placement progress. Besides standard call connection modes, there are two monitoring modes: Network Loopback and Network Continuity Test. As used herein, the following terms are accorded acronyms in common use: Network Loopback: RTP LB; Network Continuity Test: Audio LB.
The prior art discloses signalling limitations inherent in MGCP/NCS architecture. The invention enables use of the MGCP/NCS protocol: by attaching a tag, such as a prefix or suffix, to the remote address, e.g. a phone number, the dumb gateway can signal connection mode to an intelligent CA. Signalling limitations in the MGCP/NCS protocol with respect to establishing connection across a network using multiple technologies are addressed by using a numbering plan which is supported by analog, TDM and packet based signalling protocols, including PSTN (SS7), ISDN (Q.931) and Internet (MGCP, SIP).
The prior art teaches away from the use of MGCP outside the Internet. This invention profits from the fact MGCP supports the same numbering plan as other legacy signalling protocols to expand the architecture of the services.
The prior art discloses solutions which differ from the system and method of the invention. In the prior art, for example,                a special signalling protocol may be put in place between the test device and the CA allowing the test device to communicate the desired connection mode to the CA, and        a connection may be established between the test device and the endpoint device in a standard connection mode from a point of view of the CA, but the test device communicates directly the loopback mode to the endpoint device via special SDP attributes, a solution which is particular to a packet-based network.        
The second solution of the prior art has been described in a draft from the Internet Engineering Task Force (IETF). A special extension is required on the SDP standard in order to add loopback connection modes. This solution is generic and may be used for different IP-based signalling protocol using SDP for media description, e.g., MGCP, SIP.
A need has been felt, because of limitations inherent in the prior art, to adapt the MGCP/NCS protocols to hybrid networks in which an endpoint is outside the IP network.
The invention describes a system and method of establishing a connection in loopback mode in the MGCP/NCS protocol so as to enable communication between remote endpoints of a network comprising diverse protocols. A test device sends traffic through the network under test, towards an endpoint termination which loops the traffic back to the test device. The termination endpoint may incorporate specific test and measurement software or/and hardware installed permanently or temporarily by technicians in the peripherals of a network to test or troubleshoot some problems, or a customer-owned device such as a cable modem.
The test device or other management entity analyses data and determines the quality of the end-to-end two-way transmission. The technique widely used for legacy Public Switched Telephone Networks (PSTN) and Integrated Services Digital Networks (ISDN), namely for Trunk testing. However, it is still not yet implemented on hybrid networks implying at least one packet-based network, waiting for enabling technologies. This invention makes a contribution towards implementing loopback testing for IP-based services.
Advantages of the system and method of the invention include:                availability of the native MGCP loopback modes;        no extension to existing protocols is required;        no substantive change is required on the MGCP/NCS capable endpoint, with limited preconfigured information on a switch;        the invention is not IP dependant. Therefore, it may easily be used by test devices on different access networks;        improved scalability of the network or networks;        improved affordability and appeal to subscribers with standard MTA, mass marketed products;        improved timing of delivery.        